Some Syrian supporters of President Bashar Assad have marked their ballots in blood as they voted in presidential elections.

On Tuesday, they pricked their fingers with pins in a symbolic act of allegiance and patriotism.

Millions of Syrians pledged renewed allegiance to Assad as they voted across government-controlled parts of the country.

Many said that re-electing Assad would give the Syrian leader more legitimacy to find a solution to the devastating three-year conflict that activists say has killed more than 160,000 people, about a third of whom were civilians.

The balloting is only taking place in government-controlled areas and Assad's win would give him a third seven-year term in office, tighten his hold on power and likely further strengthen his determination to crush the insurgency in the country.

The vote is also Syria's first multi-candidate presidential election in more than 40 years and is being touted by the government as a referendum measuring Syrians' support for Assad.